keel Lift vs side Force help???

[lordrailie]

I'm trying to calculate the area needed for a keel for a 60 foot yacht.

My sail plan give a side force of 9312 N at a Apparent wind angle of 27º and a wind speed of 9.5m/s, so if I'm not wrong I'm looking for a keel that makes a lift of a 9312 N at a yaw angle about 5º.

The thing is that I'm getting very low Lift values for my keel

The data I'm using is:

Tk 1,7
Chord Top C1 2
Chord Bottom C2 1,5
Sweep Angle 21

AR keel 0,971428571
Main Chord Keel 1,75
Taper Ratio λ 0,75
Area Keel 2,975

CL 2d foil 0,11
α degrees keel 5
CL Keel 0,179807692
CDI 0,010593898

And getting those lift and drag values, but those are not large enogh, and the keel is quite large already, and the sction is a naca 63A012

Drag 186,7417686
Lift 3169,523279

What I'm doing wrong....

Thanks

[jehardiman]

63A012 and AOA=5 degrees? Offhand, I think you are out of the drag bucket. Try it with a NACA 0012. remember that low drag is not equal to high lift.

[lordrailie]

Theoretically the lift formula should be

L= 1/2*Cl* p*S*V^2 Where p is density

And the Cl obtained from:

Cl= Cl2d*α/(1+(2/AR))

AR=Tk/C
where Tk is draft and C is chord

but .... which Tk should I consider, the depth from bottom of hull to bottom of keel or double this size (mirror with hull),

Am I right.??..

Where can I find a sample of a calculation of lift and drag of a keel, done by "hand"

Regards

[Raggi_Thor]

You can mirror it, OK.
Does that help?

[lordrailie]

If I use the whole span inclduing the mirror, the results get a lot better, but i'm not sure if they are right....

Below are the results (and data used), and the lift is 3 times larger than using only the span of the keel below the hull....

Tk 3,4
Chord Top C1 1,7
Chord Bottom C2 1,25
Sweep Angle 21

AR keel 2,305084746
Main Chord Keel 1,475
Taper Ratio λ 0,735294118
Area Keel 5,015

CL 2d foil 0,11
α degrees keel 5
CL Keel 0,294488189
CDI 0,011975647

Drag 355,8513674
Lift 8750,593853

Thanxs

[lordrailie]

any one can give mi a hint?